import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main1 {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

            int n = in.nextInt();
           long []dp=new long[n+1];

           dp[1]=1;
           if (n>=2){
               dp[2]=2;
           }

           for (int i=3;i<=n;i++){
               dp[i]=1;
               for (int j=1;j<i;j++){
                   dp[i]+=dp[j];
               }
           }
        System.out.println(dp[n]);
        }
    }
